The present invention relates to a chuck suitable for high voltage testing for a semiconductor wafer, and, more particularly, to wafer chuck designs having improved performance over a range of operating temperatures and testing conditions.
Processing semiconductor wafers include processes that form a large number of devices within and on the surface of the semiconductor wafer (hereinafter referred to simply as “wafer”). After fabrication, these devices are typically subjected to various electrical tests and characterizations. In some cases, the electrical tests characterize the operation of circuitry and in other cases characterize the semiconductor process. By characterizing the circuitry and devices thereon, the yield of the semiconductor process may be increased.
Wafer chucks used for high voltage testing may be required to operate across a wide range of temperature while exhibiting sufficient performance characteristics such as, for example, thermal uniformity across the surface of the chuck in contact with the wafer or device under test (OUT), suitable thermal transition time for the particular tests performed, adequate flatness of the chuck surface over the range of temperatures used, and low AC and DC electrical noise. Typically, wafer chucks are designed to hold the wafer or device under test using a vacuum, and such chucks require substantial supporting structure and associated equipment for accurately positioning the device under test in a controlled manner and for doing so within a controlled environment.
Changes in chuck design to accomplish a particular requirement may have adverse effects on costs, quality and/or testing processing times. For example, adding material to the chuck may increase costs for the particular material added, require additional thermal controls (such as additional chiller equipment for the probe station), add testing processing time due to an increase in thermal mass and decrease thermal transition time, contribute non-uniformities in thermal characteristics to the devices under test (thus decreasing testing quality and accuracy), and add to the overall physical space requirements within the probe station (causing other components to require resizing or increased sizes).
What is needed, therefore, are improved chuck designs that address these and other challenges. The foregoing and other objectives, features and advantages of the invention will be more readily understood upon consideration of the following detailed description of the invention taken in conjunction with the accompanying drawings.